The present invention relates to thermal ink jet printheads and more particularly, to a method and apparatus for the removal of residual ink collected on the printhead nozzle face during a printing operation by using a wiper blade and a backstop receptacle to collect the residual ink flicked from the wiper blade and to clean the wiper blade. Inadequate cleaning of the residual ink from the printhead nozzle face will result in misdirected ink droplets and subsequent print quality defects by the printhead. Inadequate cleaning of the wiper blade results in recontaminating the nozzle face with residual ink, while residual ink removed from nozzle faces by wiper blades usually flick the residual ink around resulting in the contamination of the platen holding the printing medium and the printing medium.
Thermal ink jet printing systems use thermal energy pulses generated by the heating elements in an ink jet printhead to produce momentary ink vapor bubbles on the heating elements which eject ink droplets from the printhead nozzles. One type of such a printhead has a plurality of parallel ink channels, each communicating at one end with an ink reservoir and having opposing open ends which serve as nozzles on the droplet emitting face of the printhead. A heating element, usually a resistor, is located in each of the ink channels a predetermined distance upstream from the nozzle openings. The heating elements are individually driven with a current pulse to momentarily vaporize the ink and form a bubble which expels a droplet of ink. A meniscus is formed at each nozzle under a slight negative pressure to prevent ink from weeping therefrom.
One method of fabricating an ink jet printhead having a plurality of droplet emitting nozzles therein, consists of combining an upper substrate containing one or more ink reservoirs, a lower substrate having an array of heating elements on one surface thereof, and a patterned layer of polyimide between the upper and lower substrates. The substrates, when aligned and bonded with the patterned layer of polyimide therebetween, define ink channels which are in fluid communication with the ink reservoirs at one end and are open at the other end to serve as nozzles in what are referred to as nozzle faces or front faces. The operation of a typical thermal ink jet printer is described, for example, in U.S. Pat. No. 4,849,774.
Once the individual printheads have been separated from the bonded silicon wafers by a dicing operation, the front faces thereof can be plasma cleaned to remove any polyimide debris that has been smeared in or around the nozzles by the dicing operation. Next, an amorphous or diamond like carbon (DLC) coating can be deposited on the front face of the printheads and subsequently fluorinated as in U.S. Pat. No. 5,073,785 to provide for a hydrophobic surface which prevents ink from accumulating around the nozzles and affecting the trajectory of ink droplets expelled from the nozzles.
The carriage type ink jet printer of which the present invention relates typically has one or more small printheads containing the ink channels and nozzles in a nozzle face. The printheads are combined with ink supply tanks to form an ink cartridge. In one type of cartridge, the printhead and one or more ink tanks are an integral part thereof and the entire cartridge is disposable when the ink in the tanks is depleted. In another type of cartridge, the printhead is an integral part of a replaceable ink tank support and replaceable ink supply tanks are inserted into the ink tank support. Generally, the ink tank support is first installed on the printer""s translatable carriage and then the ink tanks are installed. If the ink jet printer is a multicolor type, the replaceable ink tank support should not need to be replaced until at least ten ink supply tanks of the same color ink are depleted of ink during printing operations. Whether the carriage type ink jet printer uses replaceable ink cartridges with integral printheads that are installed on the printer""s carriage and disposed of when depleted of ink or replaceable ink tank supports with integral printheads that are installed on the printer""s carriage with separate replaceable ink supply tanks installed in the ink tank support, both types are translated in a printing zone in one direction to print a swath of information on a recording medium, such as paper. The swath height is equal to the length of the column of nozzles in the printhead""s nozzle face. The paper is held stationary during the printing and, after the swath is printed the paper is stepped a distance equal to the height of the printed swath or a portion thereof. This procedure is repeated until the entire page is printed. For an example of typical ink jet cartridges, refer to U.S. Pat. No. 4,771,295 for disposable ink tanks with integral printheads, and refer to U.S. Pat. No. 5,971,531 for replaceable ink tank supports with integral printheads and separate replaceable ink supply tanks.
As is well known, the ink jet printheads of the carriage type printers require maintenance usually at a maintenance station located to one side of the printing zone, where the printhead nozzle faces are periodically cleaned during and after a printing operation and capped to prevent the ink in the nozzles from drying out when the printer is not printing. In addition, the printhead may be primed while capped to ensure that the printhead channels are completely filled with ink and contain no print inhibiting air bubbles. The cleaning of the printhead nozzle faces are generally accomplished by using wiper blades which wipe the nozzle faces as they enter and/or leave the maintenance station. Refer to U.S. Pat. No. 5,404,158 for a typical maintenance station.
As disclosed above and in conventional carriage type ink jet printers, wiper blade cleaning of printhead nozzle faces by using the carriage motion to move the printhead nozzle face past a fixed wiper blade are well known. However, a key element to adequate cleaning is the use of appropriate high pressure contact of the wiper blade with the nozzle face. This is necessary to prevent xe2x80x98hydroplaningxe2x80x99 which leaves a film of ink and ensures sufficient wiping off of the residual ink which tends to accumulate on the nozzle face during printing. Unfortunately, high pressure contact of the wiper blade with the nozzle face results in stored energy in the deformed wiper blade as it wipes across the nozzle face, so that when the wiper blade breaks contact with the nozzle face at the end of the wiping operation, the stored energy in the wiper blade causes the ink cleaned from the nozzle face to be flicked or catapulted from the wiper blade. This flicked ink splatters onto the carriage and printing platen and any build up of ink on printer parts adjacent the paper can contact the paper and cause printed image smear. This invention solves the problem of both flicked residual ink from the wiper blade and the cleaning of the wiper blade itself.
It is an object of the present invention to provide for more effective cleaning of residual ink from the printhead nozzle face by a combination of printhead wiper blade and backstop receptacle which collects residual ink removed by the wiper blade and cleans the wiper blade.
In one aspect of the invention, there is provided a method of removing residual ink from an ink jet printhead nozzle face with a wiper blade, collecting residual ink removed, and cleaning residual ink from said wiper blade, comprising the steps of: moving the printhead nozzle face in a first direction passed a relatively stiff wiper blade, so that the wiper blade contacts said nozzle face and is flexingly deformed thereby; removing the residual ink from said nozzle face and at least partially onto said flexingly deformed wiper blade as said wiper blade is moved past said nozzle face, thereby wiping said nozzle face clean; flicking at least some of the removed residual ink from said wiper blade as said wiper blade is moved out of contact with said nozzle face, whereby said wiper blade straightens out from being flexingly deformed; collecting said at least some of the residual ink flicked from said wiper blade into a backstop receptacle; and continuing to move the nozzle face is said first direction until said wiper blade is placed into flexingly deformed contact said backstop receptacle, so that a portion of said wiper blade is wiped against the backstop receptacle, thereby cleaning all remaining residual ink therefrom.
In another aspect of the invention, there is provided in an ink jet printer having a translatable printhead with nozzles in a nozzle face from which ink droplets are ejected therefrom, said printer having means to translate the printhead, a wiper blade means for removing residual ink from the printhead nozzle face, and means for both collecting removed residual ink and cleaning the wiper blade means, comprising: said wiper means including a wiper blade fixedly mounted at one end in a positionable blade holder and having a free, opposing distal end for cleaning the nozzle face; said printhead being attached to a removable ink tank support structure, said structure being selectively translated between a printing location and a non-printing location; said positionable holder being located adjacent the non-printing location and being extendably positionable from a non-cleaning position to a cleaning position; means for selectively moving said positionable holder from said non-cleaning position to said cleaning position and returning the holder to said non-cleaning position, so that said wiper blade distal end relatively stiffly contacts the printhead nozzle face and is deformed thereby, when the ink tank structure with the printhead is translated from the non-printing location to said printing location, the wiper blade distal end wiping residual ink from the nozzle face during deformed contact therewith as said ink tank structure is being translated; a backstop receptacle for collecting residual ink flicked from the distal end of the wiper blade when the ink tank structure is translated toward the printing location from the non-printing location and said deformed wiper blade is moved out of contact with the nozzle face thus enabling the wiper blade distal end to straighten out after being deformed during contact with the printhead nozzle face; and said wiper blade distal end contacting the backstop receptacle as the ink tank structure continues translation from the non-printing location, thereby cleaning the remaining residual ink therefrom into said backstop receptacle.